When certain lytic viruses such as mengovirus infect their host ceel, host, but not viral, protein synthesis is inhibited. The double stranded replicative form of the viral RNA is thought to be involved in the inhibition, and the initiation step of protein synthesis is considered to be a likely target. The mechanism of host protein synthesis shut-off and viral protein synthesis turn-on will be studied in detail. Initiation factors will be isolated from both uninfected and infected L-cells and Ehrlich ascites tumor cells and compared in terms of their ability to stimulate globin and mengovirus RNA translation. The affinity of double stranded mengovirus RNA for host initiation factors will also be monitored.